webdevfv - 10:07 pm on Jul 3, 2013 (gmt 0)
We were running campaigns over many years and recently I did an analysis using the google adwords data on cost per conversion per hour. The costs during the night were very high compared with daytime and therefore I have now stopped adwords showing at all during 10.00pm - 6.30am.
Some businesses, i.e. sleep problem products, will actually have brilliant cost per conversion figures during these hours so make sure you test your data.